Conventional scroll compressors are designed around involutes of circles. Because this design is inherently eccentric in shape it presents disadvantages in minimizing the size of the compressor since an enclosing diameter which is drawn on center with the wrap will necessarily include some unused space in the outer periphery. As exemplified by U.S. Pat. Nos. 4,303,379, 4,304,535, 4,477,239 and 4,494,914, shifting the center of the scroll geometry has been employed in an attempt to reduce compressor size. Shifting the center of the scroll geometry is of limited potential, however, since it induces undesired torque fluctuations by shifting lines of action of compression forces. Additionally, you will still have unused space in the outer periphery which could be better used for compressor displacement.
In conventional scroll design, each set of pockets in the scroll set shares identical starting and ending angles. This results in pocket pairs of identical volume and volume ratio. U.S. Pat. No. 4,417,863 discloses a scroll design with unequal starting and ending angles, but the scroll geometry is otherwise conventional and the suction pockets have different displacement volumes.